I'd wager that SSD controllers are vastly different, one from another, in how they read/write the NAND than HDD controllers, which support the current generations of platter and head technology.
That controller, implementing multiple channels (as many as 32 in even prosumer drives) to the multiple die under various rubrics (RAISE in SandForce speak), moves the data around as needed for wear leveling.
Some controllers level more aggressively than others, but the basic structure remains the same: there is no, on purpose, contiguous (i.e., sequential) storage in an SSD
. The bits are strewn over available dies by the controller in the way it finds most efficient.
The extent to which sequential reads appear faster than random reads is due to SSD resident caching
(sometimes DRAM, sometimes NAND) and read-ahead, not defragging.
My guess, and it's only that since I don't write Windows code, is that the defrag process only gets as far as the FTL in the SSD controller
. As such, the NAND die never see the process.